Traffic-light modulator



July 11, 1950 G. B. COOK 2,514,313

TRAFFIC-LIGHT MODULATOR Filed Dec. 3, 1946 sis 40 p65 55 Ac es 6L A A 62 6o 59 53 57 56 Flea INVENTOR. A.C. GEORGE a COOK ATTORNEY.

Patented July 11, 1950 UNITED STATES PATENT OFFICE TRAFFIC-LIGHT MODULATOR GeorgeB. Cook, Philadelphia, Pa.

Application December 3,1946, Serial No. 713,728

' 4 Claims. (01. 3.15166) (Granted under. the act of March 3, .1883, as

amended April 30, 1928; 370 0. .G. 757) This invention relates to new and useful im- H particularly to a device that operates in con-.

nection with any commercial control using electric lights of various combinations and colors for vehicular and pedestrian traffic control.

It is common knowledge that a light which is of the flashing type is more conspicuous than one which shines with a constant brilliancy, especially is this true during periods of poor visibility, such as in foggy or rainy Weather when pavements and road surfaces may be wet causing reflections to be more noticeable.

It is also an established fact that incandescent electric lamps when operated with an impressed voltage of less than that for which designed, for normal brilliancy, give much longer lamp life than when operated at designed voltage and brilliancy. The device of this invention varies the impressed voltage across a bank of electric lamps flashing signal that allows the said lamps to operate for a portion of the time cycle at a voltage that is lower that that for which designed, thereby increasing the lamp life. Under favorable circumstances, and especially at night, it is even possible to operate the lamp for a portion of the cycle at a voltage below the rated voltage of the lamp, and for the remainder of the cycle at a still lower voltage, thereby prolonging its life still further. This is possible because of the increased attention attracting property of a light of frequently varying brilliancy. An incandescent electric lamp, of any commercial design and manufacture, depends as to its lamp life on the temperature at which'its filament is maintained while in use and this temperature depends, to a large degree, on the impressed voltage at the filament terminals as compared to that for which any given lamp is designed, the lower the impressed voltage, the longer the lamp life and the less the brilliancy.

In order to accomplish the objects of this invention a circuit breaker is caused to make and break a circuit, automatically, by means of a. self-starting oscillating arm that opens'and closes a pair of contact points which cut in and out a resistance in the solenoid operating circuit so that the said solenoid is energized and partially deenergized in a-time cycle the amount of said deenergization depending upon the amount of resistance being cut in and out of the said solenoid circuit. As the solenoid operated arm oscillates to 'cut in and out the resistance in the solenoid operating circuit, it also opens and closes other contacts for circuits which out other resistors in and out of the light .circuits of a. traflic control system; for instance, so that the said lights shine with a greater or lesser brilliancy:according to the voltage impressedupon them with their respective resistors being cut in or cutout. This ives a flashing eiiect to the light being emitted from the lamp in each circuit, thus controlling the brilliancy of the flash according to the amount of resistance as cut in and cut out ofeach of the circuits involved.

The principal object of this invention is to prolong the life of any incandescent lamp when used in any commercial traffic control system.

Another object of this invention is to so operate a trafllc signal byuse of a varying brilliancy of the traflie signal incandescent lamps as to make said traffic signal more conspicuous. This is especially desirable when sunlight is striking the trafiic signal, at which time it is oftenvery difficult to diflerentiate between a lighted and an unlightedtraific lamp.

Still another object of this invention is -to cause atraffic signal to .be more directive, to one whose color perception is below normal, by means of a difference in the frequency of the changes in brilliancy between the various colored lights as used-in the said traffic signal.

These and other objects of the invention, and the various features and details of the construction, operation and use thereof," are hereinafter more fully set forth and described withrefer'ence to the accompanying'drawing in which:'

Fig. 1 is a'diagrammatic View of a complete light flashing circuit, to be used with a standard traflic control system, which operates on any standard lighting voltage such as 115 volts alternating current, for instance.

- Fig. 2 is a diagrammatic View of a'power operated double cam clock circuit, for instance, to make and break contact mechanism for cutting in and out resistors in the lighting circuits, said resistors being so arranged that one stays in the circuit for long periods of time, as during the hours of darkness, operated by the clock timing mechanism, andv the other operated by cam, clock-driven, so as to cut in and cut out a resistor that will cause the lamps of a standard traffic control system to flash both during the daylight hours, when the said first resistor-"is cut out,- and at night when the said first resistor is cut The two cams shown in this schematic diagram operate at the same R. P. M. but they do not have the same number of dwells, so that the frequency of'the flash of light differs in the circuits as controlledby each cam.

3 is a diagrammatic view of a flashing light circuit with a single cam operated, clock driven mechanism for use with any standard traflic control system.

Fig. 4 is a schematic view of a crank operated variable impedance used to periodically vary the brilliance of incandescent lamps inany, standard traffic control system.

In Fig. l, a source of alternating or direct current voltage is impressed at circuit terminals I, preferably the grounded side of said circuit terminals I being connected to resistor 6 and to contact points 2 by wire 3, spring 23 and arm 8. When the contact points 2 are closed, current passes through wire 26, resistor 6, wire 2Ta'nd finally wire to energize solenoid 4, which attracts core 2| to open contacts 2. contacts 2 are opened, current passes-from the upper part of wire 3, through resistor 6, wire 2! and 5, partially deenergizing solenoid 4 because of the drop in voltage caused-by its passage through resistor 6. After passing through solenoid 4 the circuit is completed to the ungrounde side of terminals I by wire 1'.

The frequency of the cycle of operation caused by the making and breaking of contact 2 in circuit I may be varied by varying the length and weight of arm 8 in relation to the stiffness of the supporting spring 23, which is attached to a base by means of post 22. and closed by the action of solenoid 4, arm 8 oscillates, and alternately opens and closes contacts 9 and ID, by means of the blocksof'insulating material 24 and 25. As contact 9 opens and closes, wires 12 and I3 cut resistor M in and out of circuit 20, thereby varying the potential across lamp II which may,'for instance, be in a green light circuit of a standard traiiic control system. This potential variation will cause a variation in brilliancy or flickering efiect in green light I I, timed by the opening and closing of contact points 9. In a like manner, contact points I'll control circuit l9 through wires l6 and I! and resistor l8, varying thebrilliancy of lamp I5, and said circuit I9 may be, for instance, a red light circuit in any standard traffic control system.

As shown in Fig. 2, a source of potential is impressed at circuit terminals designated by numeral 28, preferably the ungrounded side of circuit 28 being connected to a lamp-bank circuit 30, for instance, by wire 29 and the grounded side of said circuit 28 connected to a clock operated timer 39 by wires 35 and 36, so that resistance 33 is cut in and out at at long intervals of time, such as in from dusk to dawn, and out from dawn to dusk, so that during the daylight hours the lamps are operated at a higher brilliancy than during the hours of darkness when the resistance 33 is cut in to circuit 28 so that lamps in circuit 30 burn at a lower brilliance. Circuit 28 is also connected to a resistance 3| by wires 32 and by means of wire 31 contact 38 and wire 46 resistance 3! is cut in and out of circuit 28, so as to cause the lamps of circuit 30 to flash at a relatively high frequency regardless of whether resistor 33 is in or out of the circuit. Further, circuit 52 is operated in the same manner as is circuit 28 of Fig. 2, but having cam 40 with, for example, one dwell operating contact 4|, so that the frequency of flashing of lamps in circuit 41 is one-half that of lamps 30 in circuit as operated by cam 42, having two dwells, for example. It is important that contacts 38 and 4| be electrically insulated from cams 42 and 40. Because of this difference in frequency of flashing as produced in the two cir- When said operate from a clock mechanism 65 that includes a contactor (not shown), which cuts resistor 58 in and out of circuit 55 by means of wires 57 and 59, thereby controlling the long time brilliancy cycle of lamps in circuit 63, while cam 40, by means of contactor 66 and wires GI and 64, cut resistor 62 in and out of circuit 55 and thereby controlling the timing of flashing cycle of lamp circuit 63. The circuit shown in Fig. 3 could be used to control or modulate say, one red or stop light circuit. Obviously, one Or more sets of .contacts, (not shown) could be made to bear As contact 2 is opened on cam Ml so as to control or modulate other similar circuits at the same frequency with or without extra clock contacts (also not shown) and these may be, for example, green or "go and amber or caution light circuits.

As shown in Fig. 4 a crank arm 68 revolves about a center 61 being driven by an electric motor, for instance, and attached to link l8 by pin 69 and to a suitable metal core H by pin 12, so that the metal core ll moves transversely to the wires of a reactance coil 13 and thereby varies the impedance set up in circuit 16 through wires 18 and M and lamp [5 which variable impedance, in turn, varies periodically the impressed voltage on lamp l5 and the brilliance of said lamp.

While a particular embodiment of this invention has been illustrated and described herein, it is not intended that this invention be limited to such disclosure, and changes and modifications may be made and incorporated within the scope of the claims.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What I claim is:

l. The method of operating a traflic-control signalling system having differently colored incandescent lamps for indicating stop and go conditions that comprises the steps of applying a periodically varying voltage to said lamps to cause them to emit light of varying intensity corresponding to the voltage variations, thereby to diminish substantially the average heating effect to which said lamps are subjected, and additionally diminishing the voltage applied to said lamps when the ambient light condition falls below a predetermined light value, thereby further reducing the average heating effect on said lamps.

2. The method of operating a traflic signalling system having characteristically colored incandescent lamps disposed in a medium having a diurnally variable mean ambient light intensity for indicating stop and go conditions, comprising applying a periodically varying voltage to said lamps to cause them to emit varying lights of intensity at least as great as a predetermined mean ambient light intensity, and uniformly diminishing the voltage applied to said lamps when the mean ambient light intensity falls below a predetermined minimum value.

3. A diurnally compensated trafiic-control signalling system comprising first and second incandescent lamps, circuit connections including a source of electrical energy connected to energize said lamps to emit light of different col ors, thereby to indicate different traffic conditions, individual electric current varying means in respective ones of said lamp circuits, means periodically actuating said current varying means at different frequencies, thereby varying the intensity of the light emitted by said lamps at frequencies corresponding to different traflic conditions, and means for periodically and uniformly varying the current in each of said circuits at a frequency substantially lower than either of said different frequencies.

4. The system as in claim 3 wherein said first and second lamps are disposed in a region characterized by a diurnal variation in ambient light conditions, said system further comprising individual resistors having equal resistance values in each of said lamp circuits, and said means for uniformly varying the currentjn each of said circuits comprising time-controlled switching 6 means for simultaneously switching said individual resistors into or out of said circuits when the ambient light conditions rise above or fall below a preselected ambient light value.

GEORGE B. COOK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS.

Number Name Date 976,287 Phelps Nov. 22, 1910 1,122,975 Miller Dec. 29, 1914 2,053,155 La Roque Sept. 1, 1936 2,132,097 Bryant Oct. 4, 1938 2,320,483 Stocker June 1943 2,335,076 Neumueller Nov. 23, 1943 2,407,113

Tuck Sept. 3, 1946 Certificate of Correction Patent No. 2,514,373

July 11, 1950 GEORGE B. COOK It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 1, line 21, before the Word flashing insert so that the brilliance varies, thus causing a; line 23, for lower that read lower than; column 3, line 54, strike out "at, first occurrence; and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Office. Signed and sealed this 7th day of November, A. D. 1950.

[SEAL] THOMAS F. MURPHY,

Assistant Commissioner of Patents. 

